Temporary immobilization and a number of medical procedures subject the patient to the risk of pulmonary embolism. This risk can be significantly reduced by the use of a filter implant. Currently available filter devices are not easily or safely removable after they have remained in place for more than approximately two weeks. The use of a permanent filter device would not be desirable when temporary protection against pulmonary embolism is needed, especially in younger patients. A temporary filter device that can be easily and safely removed after the threat of pulmonary embolism is over is most desirable.
Temporary blood clot filters are well known as evidenced from the following non-exhaustive list of prior publications and U.S. Patents (the entire content of each being expressly incorporated hereinto by reference): Hagspiel et al, “Inferior vena cava filters: An update”, Applied Radiology, pp. 20–34 (November 1998); U.S. Pat. No. 6,007,558; U.S. Pat. No. 5,984,947; U.S. Pat. No. 5,976,172; U.S. Pat. No. 5,893,869; U.S. Pat. No. 5,836,968; U.S. Pat. No. 5,853,420; U.S. Pat. No. 5,836,969; U.S. Pat. No. 5,928,261; U.S. Pat. No. 6,051,015; U.S. Pat. No. 5,746,767; U.S. Pat. No. 5,634,942; U.S. Pat. No. 5,626,605; U.S. Pat. No. 5,601,595; U.S. Pat. No. 5,415,630 and U.S. Pat. No. 5,383,887.
While a variety of proposals for removable blood clot filters exist in the art, improvements are still desired. For example, it would especially be desirable if a temporary blood filter could be implanted in a patient's inferior vena cava and remain therein for a reasonable time, yet be capable of withdrawal without causing damage to the vessel wall. It is towards fulfilling such a need that the present invention is directed.
Broadly, therefore, the present invention relates to a blood filter which is sized and configured to be positioned within a vascular vessel comprising a plurality of anchoring arms for temporarily anchoring the blood filter to a wall of the vascular vessel. Importantly, the anchoring arms include a removable sleeve. In especially preferred embodiments, the removable sleeve is formed of a bioabsorbable material. Thus, when the filter of the present invention is deployed, it is this removable sleeve which comes into contact with the inner tissue wall of the patient's blood vessel (typically the inferior vena cava). When it is desired to remove the filter, endothelization of the sleeve has typically occurred but since the sleeves are a removable (separable) component part of the anchoring arms, the entire filter device can be retrieved thereby leaving the endothelized sleeves remaining in place on the interior wall of the patient's blood vessel. However, such sleeves will be absorbed over time (preferably by means of hydrolysis) since they are formed of a bioabsorbable polymeric material. In such a manner, the filters 10 of the present invention allow relatively easy retrieval while minimizing (if not preventing entirely) harm to the vascular endothelium.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.